add UMA metrics for voice interaction entries.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index c9ff8801f5d904a9953c0192f36f97000e90d549..fda2e2052d6d311ff76cfab296be90f12dc00f51 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -79569,6 +79569,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="VoiceInteraction.EntryPoints" enum="VoiceInteractionEntryPoints">
+  <owner>muyuanli@chromium.org</owner>
+  <owner>zalcorn@chromium.org</owner>
+  <summary>
+    Records the frequency users access voice interaction by each of the
+    entry point.
+  </summary>
+</histogram>
+
+<histogram name="VoiceInteraction.MetaLayer.EntryPoints" 
+           enum="VoiceInteractionMetaLayerEntryPoints">
+  <owner>muyuanli@chromium.org</owner>
+  <owner>zalcorn@chromium.org</owner>
+  <summary>
+    Records the frequency users access voice interaction meta layer by each 
+    of the entry point.
+  </summary>
+</histogram>
 <histogram name="VRDisplayPresentResult" enum="PresentationResult">
   <owner>billorr@chromium.org</owner>
   <summary>